1. Field of the Invention
This invention relates to equipment intended for use in down hole environments, such as may typically be found in oil and gas wells. The invention has a particular application in connection with well casing cleaning apparatus.
2. Background of the Related Art
In U.S. Pat. No. 5,711,046, there is described well cleaning apparatus which has a body member to which is attached, preferably, a plurality of cleaning pads spaced circumferentially around the body member. The pads are provided with bristles on their outer face and are biased outwardly by coil springs or similar means in an attempt to maintain a sufficient contact pressure of the bristles on the interior wall of the casing.
British Patent Number GB 2,295,632 describes an alternative brushing tool which incorporates bristles that protrude from raised rib-like portions on a body member.
An alternative well clean up tool is generally known as a casing scraper. This type of tool typically incorporates casing scraper blades that scrape the inside of the casing or tubing in the well. The steel blades may also be mounted on detachable pads, plates or the like.
An object of the present invention is to provide an improved means of retaining pads supporting brushes, scraper blades or the like.
There are several operations performed down-hole that may lead to the wear or damage of particular components of a tool. The present invention therefore recognizes that it would be advantageous to design a means for the easy and cost efficient replacement or repair of such components. An object of the present invention therefore is to provide certain components prone to premature wear or damage in a manner which allows them to be detached from the main body of the tool. Moreover, a related and yet further object is to provide an improved retaining means for retaining detachable components or consumables to the body of a respective down-hole tool.
The retaining means should allow for the convenient and efficient removal and replacement of a component or consumable, while also allowing for the effective use and operation of the component during the normal operation of the tool.
An example of the type of component that has been found advantageous to retain in a detachable manner is a pad used to support bristles on a casing brush. A casing brush or brushing tool as it is also known in the industry is a type of well clean up tool, designed for producing a clean interior in the casing or liner of the drilling well. The pads support a bed of wire bristles and are typically biased outwardly by compression springs or the like that cause the bristles to bear forcibly on the casing wall. The pressure of the pads on the casing lead to the wear of the bristles and warrants bristle replacement or repair.
According to the present invention, there is provided a down-hole tool comprising a generally tubular body member and one or more detachable pads, the one or more pads each being retained to the body member by a retaining means provided as a plurality of longitudinal mechanical fasteners disposed in generally radial orientation in use and positioned so as to correspond with and pass through respective apertures provided in the pads, wherein the mechanical fasteners each engage the body member and limit the radial movement of the pad away from the body member.
Preferably each pad is provided with a said aperture in the vicinity of each of its corners and is retained in use to the body member by a mechanical fastener at each said aperture.
Typically the mechanical fasteners are bolts or threaded rods. They may be formed with a bolt head or may be associated with retaining nuts or the like. The apertures may be countersunk on the outer face of the pad to provide a recess for the bolt head or retaining nut.
The tool may further include biasing means for biasing the or each pad in an outward radial direction, wherein the biasing means comprise springs held under compression in use.
The springs may be coil springs or leaf springs for example. Preferably, where the springs are provided as coil springs, some or all of the springs may be located over the mechanical fasteners. In any event, the springs are preferably located toward the peripheral edges of the pad. This has the advantage of promoting an even or balanced outward bias on the pad.
Typically, the pads support one or more cleaning members on their outer face for cleaning casing strings. The cleaning members may be bristles or scraper blades for example.